README for XFree86 3.3 on NetBSD and OpenBSD : Kernel Support for X : Aperture Driver
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7.1. Aperture Driver

By default NetBSD 0.9C and higher include the BSD 4.4 kernel security feature that disable access to the /dev/mem device when in multi-users mode. But XFree86 servers can take advantage (or require) linear access to the display memory.

The P9000, Mach64 and AGX servers require linear memory access, other accelerated servers can take advantage of it, but do not require it.

There are two ways to allow XFree86 to access linear memory:

  1. Disable the kernel security feature by adding `option INSECURE' in the kernel configuration file and build a new kernel. On NetBSD-1.0 you have to disable kernel security by initializing the ``securelevel'' variable to -1 in /sys/kern/kern_sysctl.c, line 205. For more informations, see the comments in /usr/include/sys/systm.h.
  2. Install the aperture driver:
    1. The first step is highly dependent from your exact operating system version:
      • NetBSD 1.0, 1.1, 1.2, 1.2.1:

        Add the following lines to the end of /etc/rc.local:

         KERNDIR=/usr/X11R6/lib/X11/kernel
         if [ -f ${KERNDIR}/ap.o ]; then
           modload -o ${KERNDIR}/ap -e ap -p ${KERNDIR}/apinstall ${KERNDIR}/ap.o
         fi
        

      • NetBSD 1.2D and later

        Add the following line to /etc/lkm.conf:

        /usr/X11R6/lib/X11/kernel/ap.o  -  ap /usr/X11R6/lib/X11/kernel/apinstall - 
        

      • OpenBSD 2.0

        Use the aperture driver from /usr/lkm: set KERNDIR to /usr/lkm in the above procedure for NetBSD 1.0.

      • OpenBSD 2.1

        Uncomment the lines loading the aperture driver from /etc/rc.securelevel

    2. Reboot your system. XFree86 will auto-detect the aperture driver if available.
    Warning: if you boot another kernel than /netbsd or /bsd, loadable kernel modules can crash your system. Always boot in single user mode when you want to run another kernel.

    Caveat: the aperture driver only allows one access at a time (so that the system is in the same security state once X is launched). This means that if you run multiple servers on multiples VT, only the first one will have linear memory access. Use 'option INSECURE' if you need more that one X server at a time.


README for XFree86 3.3 on NetBSD and OpenBSD : Kernel Support for X : Aperture Driver
Previous: Kernel Support for X
Next: MIT-SHM